Dynamic Stability and Flying Qualities of an Unmanned Airplane as a Flexible Body

This paper focus on the analysis of the stability and flying qualities of the Unmanned Airplane for Ecological Conservation as a flexible vehicle. The present model uses Lagrange’s equation to develop the nonlinear equations of motion for the elastic vehicle, and aerodynamic strip-theory to obtain the expressions for the generalized forces. The mode shapes of the first six vibration modes of the structure are considered to compute the coefficients of the aeroelastic contributions to the forces and moments, which are used to obtain the eigenvalues of the dynamic modes for the flexible vehicle. The flight modes are stable regardless the number of vibration modes applied to the model, nevertheless, the characteristic values of the flight dynamic modes change when the flexible modes are considered in the model. The model is able to predict the conditions at which the system becomes unstable due to the flexible modes. Non-linear, open-loop simulations were performed and the response of the velocity, pitch angle, pitch rate and angle of attack, due to an elevator double step are presented. Results show that the flexible model has an impact on the response, and on the initial values of the variables studied